Several cancer screening studies and projects are underway or being designed to gain a better understanding of the impact and consequences of such screening in various population settings. Staff are involved in the International Prostate Screening Trials Evaluation Group, an international collaboration for the evaluation of prostate cancer screening trials. Trial investigators from Europe and North America are involved in an effort to develop a common core protocol and database so that in future years, data from various trials can be effectively combined to provide a comprehensive evaluation of prostate cancer screening. The International Breast Cancer Screening Database Working Group was initiated in the early 1990's to bring together investigators worldwide involved in implementing breast cancer screening in countries or regions. Researchers involved are from Europe, North America, South America, Japan, and Australia. The purpose of the collaboration is to provide a mechanism for the development of a common database to which participating countries would contribute so that screening programs in various countries can be compared and to evaluate the contribution of screening to breast cancer control worldwide. A new data collection undertaken in the current period focused on program characteristics and operational issues. Staff are involved in an international collaboration for the evaluation of screening for colorectal and ovarian cancers. Trial investigators from the U.S. and the United Kingdom have met to discuss common protocol and database features of their trials. It is hoped this will lead to enhanced design modification of new and ongoing trials and ultimately provide a common database so that in future years, data from various trials can be effectively combined to provide a more comprehensive evaluation of screening for these cancers than could be achieved by any single trial. Consultation on the design of a trial of screening for esophageal cancer in a region of Iran included discussion on alternatives choices of randomization unit, sample size requirements, and followup procedures. Consultation on analysis of esophageal cancer screening data from China was also done. Staff participate on the Data Safety and Monitoring Committee of the Prostate Cancer Prevention Trial which is carried out by the Southwest Oncology Group through funding from DCPC.